364 Mr. Taylor on the Smelting of Tin Ores 
tin ores, nor is there any one in which the reasons for the mode of 
treatment are so obvious. There are but two things to accomplish 
in this first process ; to obtain perfect fusion of the earths so as to 
suffer the metal to separate easily from them, and to decompose 
the oxide of which the ore uniformly consists. 
The addition of lime contributes to effect the former, and that of 
carbonaceous matter or coal completes the reduction of the ore. 
The separation of the metal from the earths then takes place in the 
usual way during fusion, by the difference in their specific gravities, 
the one precipitating to the bottom of the furnace, from whence it 
is drawn off by the tap-hole, and the other floating on the surface 
is removed in the manner I have described. 
The plates of tin, which are the produce of this smelting, are 
somewhat impure, and are more or less so according to the quality 
of the ore which has been used ; they are reserved until a sufficient 
quantity of them are obtained to proceed with the refining, which 
is performed either in the same furnace, after ore-smelting is 
finished, or in a similar one, which may be reserved for the 
purpose. 
All the processes for refining metals in the fire must be performed 
by taking advantage of some property in which the metal operated 
on may differ from those with which it is alloyed, and which it is 
intended to separate from it. These differences may consist in the 
facility or difficulty of oxidation, in their tendency to volatilize, in 
the temperature required for fusion, or in their relative specific 
gravities. 
Upon an attention to the two latter circumstances are founded 
the operation for refining tin. The substances which are most to 
be suspected in the produce of the first melting, and which it is 
desirable to separate, will probably be, iron, copper, arsenic, 
